Fix "unreliable" discovery with ippfind as used by driverless backend (Issue #1211)

- Export _cupsGetClock private API.
- Use _cupsGetClock in ippfind.
- Drop "avahi_have_data" and adopt CUPS 2.5/3.0 processing strategy.

Author: michaelrsweet

CHANGES.md

@@ -26,6 +26,7 @@ Changes in CUPS v2.4.12 (YYYY-MM-DD)
 - Fixed attributes returned by the Create-Xxx-Subscriptions requests
   (Issue #1204)
 - Fixed `ippDateToTime` when using a non GMT/UTC timezone (Issue #1208)
+- Fixed DNS-SD discovery with `ippfind` (Issue #1211)
 
 
 Changes in CUPS v2.4.11 (2024-09-30)

cups/libcups2.def

@@ -16,6 +16,7 @@ _cupsEncodeOption
 _cupsEncodingName
 _cupsFilePeekAhead
 _cupsGet1284Values
+_cupsGetClock
 _cupsGetDestResource
 _cupsGetDests
 _cupsGetPassword

tools/ippfind.c

@@ -3,18 +3,14 @@
  * commands such as IPP and Bonjour conformance tests.  This tool is
  * inspired by the UNIX "find" command, thus its name.
  *
- * Copyright © 2020-2024 by OpenPrinting.
+ * Copyright © 2020-2025 by OpenPrinting.
  * Copyright © 2020 by the IEEE-ISTO Printer Working Group
  * Copyright © 2008-2018 by Apple Inc.
  *
  * Licensed under Apache License v2.0.  See the file "LICENSE" for more
  * information.
  */
 
-/*
- * Include necessary headers.
- */
-
 #define _CUPS_NO_DEPRECATED
 #include <cups/cups-private.h>
 #ifdef _WIN32
@@ -129,7 +125,6 @@ typedef struct ippfind_srv_s		/* Service information */
 static DNSServiceRef dnssd_ref;		/* Master service reference */
 #elif defined(HAVE_AVAHI)
 static AvahiClient *avahi_client = NULL;/* Client information */
-static int	avahi_got_data = 0;	/* Got data from poll? */
 static AvahiSimplePoll *avahi_poll = NULL;
 					/* Poll information */
 #endif /* HAVE_MDNSRESPONDER */
@@ -139,6 +134,7 @@ static int	address_family = AF_UNSPEC;
 static int	bonjour_error = 0;	/* Error browsing/resolving? */
 static double	bonjour_timeout = 1.0;	/* Timeout in seconds */
 static int	ipp_version = 20;	/* IPP version for LIST */
+static double	last_update = 0.0;	/* Last update time */
 
 
 /*
@@ -170,7 +166,6 @@ static int		eval_expr(ippfind_srv_t *service,
 static int		exec_program(ippfind_srv_t *service, int num_args,
 			             char **args);
 static ippfind_srv_t	*get_service(cups_array_t *services, const char *serviceName, const char *regtype, const char *replyDomain) _CUPS_NONNULL(1,2,3,4);
-static double		get_time(void);
 static int		list_service(ippfind_srv_t *service);
 static ippfind_expr_t	*new_expr(ippfind_op_t op, int invert,
 			          const char *value, const char *regex,
@@ -1308,14 +1303,12 @@ main(int  argc,				/* I - Number of command-line args */
   */
 
   if (bonjour_timeout > 1.0)
-    endtime = get_time() + bonjour_timeout;
+    endtime = _cupsGetClock() + bonjour_timeout;
   else
-    endtime = get_time() + 300.0;
+    endtime = _cupsGetClock() + 300.0;
 
-  while (get_time() < endtime)
+  while (_cupsGetClock() < endtime)
   {
-    int		process = 0;		/* Process services? */
-
 #ifdef HAVE_MDNSRESPONDER
     int fd = DNSServiceRefSockFD(dnssd_ref);
 					/* File descriptor for DNS-SD */
@@ -1337,18 +1330,8 @@ main(int  argc,				/* I - Number of command-line args */
 
       DNSServiceProcessResult(dnssd_ref);
     }
-    else
-    {
-     /*
-      * Time to process services...
-      */
-
-      process = 1;
-    }
 
 #elif defined(HAVE_AVAHI)
-    avahi_got_data = 0;
-
     if (avahi_simple_poll_iterate(avahi_poll, 500) > 0)
     {
      /*
@@ -1359,108 +1342,103 @@ main(int  argc,				/* I - Number of command-line args */
       return (IPPFIND_EXIT_BONJOUR);
     }
 
-    if (!avahi_got_data)
-    {
-     /*
-      * Time to process services...
-      */
-
-      process = 1;
-    }
 #endif /* HAVE_MDNSRESPONDER */
 
-    if (process)
-    {
-     /*
-      * Process any services that we have found...
-      */
+   /*
+    * Process any services that we have found...
+    */
 
-      int	active = 0,		/* Number of active resolves */
-		processed = 0;		/* Number of processed services */
+    int	active = 0,			/* Number of active resolves */
+	processed = 0;			/* Number of processed services */
 
-      for (service = (ippfind_srv_t *)cupsArrayFirst(services);
-           service;
-           service = (ippfind_srv_t *)cupsArrayNext(services))
-      {
-        if (service->is_processed)
-          processed ++;
+    for (service = (ippfind_srv_t *)cupsArrayFirst(services);
+	 service;
+	 service = (ippfind_srv_t *)cupsArrayNext(services))
+    {
+      if (service->is_processed)
+	processed ++;
 
-        if (!service->ref && !service->is_resolved)
-        {
-         /*
-          * Found a service, now resolve it (but limit to 50 active resolves...)
-          */
+      if (!service->ref && !service->is_resolved)
+      {
+       /*
+	* Found a service, now resolve it (but limit to 50 active resolves...)
+	*/
 
-          if (active < 50)
-          {
+	if (active < 50)
+	{
 #ifdef HAVE_MDNSRESPONDER
-	    service->ref = dnssd_ref;
-	    err          = DNSServiceResolve(&(service->ref),
-					     kDNSServiceFlagsShareConnection, 0,
-					     service->name, service->regtype,
-					     service->domain, resolve_callback,
-					     service);
+	  service->ref = dnssd_ref;
+	  err          = DNSServiceResolve(&(service->ref),
+					   kDNSServiceFlagsShareConnection, 0,
+					   service->name, service->regtype,
+					   service->domain, resolve_callback,
+					   service);
 
 #elif defined(HAVE_AVAHI)
-	    service->ref = avahi_service_resolver_new(avahi_client,
-						      AVAHI_IF_UNSPEC,
-						      AVAHI_PROTO_UNSPEC,
-						      service->name,
-						      service->regtype,
-						      service->domain,
-						      AVAHI_PROTO_UNSPEC, 0,
-						      resolve_callback,
-						      service);
-	    if (service->ref)
-	      err = 0;
-	    else
-	      err = avahi_client_errno(avahi_client);
+	  service->ref = avahi_service_resolver_new(avahi_client,
+						    AVAHI_IF_UNSPEC,
+						    AVAHI_PROTO_UNSPEC,
+						    service->name,
+						    service->regtype,
+						    service->domain,
+						    AVAHI_PROTO_UNSPEC, 0,
+						    resolve_callback,
+						    service);
+	  if (service->ref)
+	    err = 0;
+	  else
+	    err = avahi_client_errno(avahi_client);
 #endif /* HAVE_MDNSRESPONDER */
 
-	    if (err)
-	    {
-	      _cupsLangPrintf(stderr,
-	                      _("ippfind: Unable to browse or resolve: %s"),
-			      dnssd_error_string(err));
-	      return (IPPFIND_EXIT_BONJOUR);
-	    }
+	  if (err)
+	  {
+	    _cupsLangPrintf(stderr,
+			    _("ippfind: Unable to browse or resolve: %s"),
+			    dnssd_error_string(err));
+	    return (IPPFIND_EXIT_BONJOUR);
+	  }
 
-	    active ++;
-          }
-        }
-        else if (service->is_resolved && !service->is_processed)
-        {
-	 /*
-	  * Resolved, not process this service against the expressions...
-	  */
+	  active ++;
+	}
+      }
+      else if (service->is_resolved && !service->is_processed)
+      {
+       /*
+	* Resolved, not process this service against the expressions...
+	*/
 
-          if (service->ref)
-          {
+	if (service->ref)
+	{
 #ifdef HAVE_MDNSRESPONDER
-	    DNSServiceRefDeallocate(service->ref);
+	  DNSServiceRefDeallocate(service->ref);
 #else
-            avahi_service_resolver_free(service->ref);
+	  avahi_service_resolver_free(service->ref);
 #endif /* HAVE_MDNSRESPONDER */
 
-	    service->ref = NULL;
-	  }
+	  service->ref = NULL;
+	}
 
-          if (eval_expr(service, expressions))
-            status = IPPFIND_EXIT_TRUE;
+	if (eval_expr(service, expressions))
+	  status = IPPFIND_EXIT_TRUE;
 
-          service->is_processed = 1;
-        }
-        else if (service->ref)
-          active ++;
+	service->is_processed = 1;
       }
+      else if (service->ref)
+	active ++;
+    }
 
-     /*
-      * If we have processed all services we have discovered, then we are done.
-      */
+   /*
+    * If we have processed all services we have discovered, then we are done.
+    */
 
-      if (processed == cupsArrayCount(services) && bonjour_timeout <= 1.0)
-        break;
-    }
+    if (processed > 0 && (processed == cupsArrayCount(services) || (_cupsGetClock() - last_update) >= 2.5) && bonjour_timeout <= 1.0)
+      break;
+
+   /*
+    * Give the browsers/resolvers some time...
+    */
+
+    usleep(250000);
   }
 
   if (bonjour_error)
@@ -1490,6 +1468,8 @@ browse_callback(
   * Only process "add" data...
   */
 
+  last_update = _cupsGetClock();
+
   (void)sdRef;
   (void)interfaceIndex;
 
@@ -1522,6 +1502,8 @@ browse_local_callback(
   ippfind_srv_t	*service;		/* Service */
 
 
+  last_update = _cupsGetClock();
+
  /*
   * Only process "add" data...
   */
@@ -1565,6 +1547,8 @@ browse_callback(
   ippfind_srv_t	*service;		/* Service information */
 
 
+  last_update = _cupsGetClock();
+
   (void)interface;
   (void)protocol;
   (void)context;
@@ -2190,31 +2174,6 @@ get_service(cups_array_t *services,	/* I - Service array */
 }
 
 
-/*
- * 'get_time()' - Get the current time-of-day in seconds.
- */
-
-static double
-get_time(void)
-{
-#ifdef _WIN32
-  struct _timeb curtime;		/* Current Windows time */
-
-  _ftime(&curtime);
-
-  return (curtime.time + 0.001 * curtime.millitm);
-
-#else
-  struct timeval	curtime;	/* Current UNIX time */
-
-  if (gettimeofday(&curtime, NULL))
-    return (0.0);
-  else
-    return (curtime.tv_sec + 0.000001 * curtime.tv_usec);
-#endif /* _WIN32 */
-}
-
-
 /*
  * 'list_service()' - List the contents of a service.
  */
@@ -2517,7 +2476,7 @@ new_expr(ippfind_op_t op,		/* I - Operation */
  *
  * Note: This function is needed because avahi_simple_poll_iterate is broken
  *       and always uses a timeout of 0 (!) milliseconds.
- *       (Avahi Ticket #364)
+ *       (Avahi Github issue #127)
  */
 
 static int				/* O - Number of file descriptors matching */
@@ -2527,18 +2486,10 @@ poll_callback(
     int           timeout,		/* I - Timeout in milliseconds (unused) */
     void          *context)		/* I - User data (unused) */
 {
-  int	val;				/* Return value */
-
-
   (void)timeout;
   (void)context;
 
-  val = poll(pollfds, num_pollfds, 500);
-
-  if (val > 0)
-    avahi_got_data = 1;
-
-  return (val);
+  return (poll(pollfds, num_pollfds, 500));
 }
 #endif /* HAVE_AVAHI */
 
@@ -2569,6 +2520,8 @@ resolve_callback(
 					/* Service */
 
 
+  last_update = _cupsGetClock();
+
  /*
   * Only process "add" data...
   */
@@ -2650,6 +2603,8 @@ resolve_callback(
   AvahiStringList *current;		/* Current TXT key/value pair */
 
 
+  last_update = _cupsGetClock();
+
   (void)address;
 
   if (event != AVAHI_RESOLVER_FOUND)